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CONTINUOUS BLACK CARBON MEASUREMENTS INDOORS AND OUTDOORS AT AN OCCUPIED HOUSE FOR ONE YEAR
Citation:
LaRosa, L., C HowardReed, AND L A. Wallace. CONTINUOUS BLACK CARBON MEASUREMENTS INDOORS AND OUTDOORS AT AN OCCUPIED HOUSE FOR ONE YEAR. Presented at ISEA 2000 Exposure Analysis in the 21st Century: Integrating Science, Policy and Quality of Life, Monterey Peninsula, CA, October 24-27, 2000.
Impact/Purpose:
The main objective is to investigate human exposure to fine and coarse particles (and PAHs) from several important sources such as cooking, woodsmoke, and household cleaning. A second objective is to investigate the observed increased personal exposure (compared to indoor air concentrations measured by a fixed monitor) to particles: the so-called "personal cloud," that has been observed in many occupational and some environmental studies. A third objective is to incorporate the findings into a mass-balance indoor air quality model.
Description:
Black carbon is one of the components of particulate matter, and is of importance because the only known source of aerosol black carbon in the atmosphere is the combustion of carbonaceous fuels (Hansen, 1997). Polyaromatic hydrocarbons (PAH) formed in the combustion process are generally associated with black carbon. The health effects of black carbon and associated PAHs may thus include both carcinogenicity and short-term effects associated with fine particle inhalation (e.g., decreased heart rate variability). The purposes of this study were 1) to record indoor and outdoor concentrations of black carbon every five minutes at an occupied residence over a one-year period; 2) to identify outdoor and indoor sources black carbon; and 3) to determine indoor-outdoor relationships including penetration factors and deposition rates. The residence was a three-story townhouse in a Virginia suburban location 25 miles from Washington, DC with two nonsmoking adult residents. A 10-lane toll road and airport expressway was 1.5 miles distant from the residence. Two Aethalometers (Magee Scientific Company, Berkeley, California) were used to measure simultaneous indoor and outdoor black carbon concentrations every five minutes from May, 1998 to May, 1999. After correction for an observed effect of cumulative optical depth on the Aethalometer readings, the precision of the two Aethalometers was approximately 10%. Arithmetic means (standard deviations) were 741 (611) nanograms per cubic meter outdoors and 461 (3194) nanograms per cubic meter indoors (N = 89, 771 and 94,361, respectively). During period with known indoor sources (N = 7,748 cases), the indoor arithmetic mean concentration was 1007 nanograms per cubic meter, compared to 412 nanograms per cubic meter during 86,613 cases without indoor sources. Geometric means were 573 nanograms per cubic meter outdoors and 319 nanograms per cubic meter indoors. Geometric standard deviations were 2.08 outdoors and 2.18 indoors. Peak outdoor concentrations were observed throughout the year in the 6-9 AM period, indicative of vehicular traffic. In the fall and winter months, peak outdoor concentrations were observed in the 6PM-midnight period, mostly on weekends, indicative of residential wood burning. Indoor black carbon concentrations followed the outdoor pattern, except for period when an indoor source was operating. A major source of personal exposure was found to be a Citronella which, when used as directed (within 3 feet of the person), elevated black carbon concentrations by a factor of 40-100. Analyses of Variance (ANOVA) were conducted to identify indoor and outdoor concentration patterns, and identify source. The two major indoor sources were cooking and burning candles. Linear regression analyses were conducted on the logarithms of the corrected concentrations with the following result (N=80, 760 cases; Adj. R squared = 52%):
Ln (Indoor BC) = 0.997 (0.016) + 0.745 (0.002 Ln (Outdoor BC).
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